1. Field of the Invention
The present invention relates to a plasma display panel (PDP) driver, a driving method thereof, and a plasma display.
2. Description of the Related Art
The plasma display is a flat panel display that uses plasma generated via a gas discharge process to display characters or images, and tens to millions of pixels are provided thereon in a matrix format, depending on its size. Plasma displays are typically categorized as either DC plasma displays or AC plasma displays, according to supplied driving voltage waveforms and discharge cell structures.
Since DC plasma displays have electrodes exposed in the discharge space, they allow a current to flow in the discharge space while the voltage is supplied, and therefore they problematically require resistors for current restriction. On the other hand, since AC plasma displays have electrodes covered by a dielectric layer, capacitances are naturally formed to restrict current, and the electrodes are protected from ion shocks when discharging. Accordingly, they have a longer lifespan than the DC plasma displays.
FIG. 1 shows a perspective view of an AC PDP. As shown, a scan (Y) electrode 4 and a sustain (X) electrode 5, disposed over a dielectric layer 2 and a protection film 3, are provided in parallel and form a pair with each other under a first glass substrate 1. A plurality of address (A) electrodes 8 covered with an insulation layer 7 are installed on a second glass substrate 6. Barrier ribs 9 are formed in parallel with the address electrodes 8, on the insulation layer 7 between the address electrodes 8, and phosphor 10 is formed on the surface of the insulation layer 7 between the barrier ribs 9. The first and second glass substrates 1, 6 having a discharge space 11 between them are provided facing each other so that the scan electrode 4 and the sustain electrode 5 may respectively cross the address electrode 8. The address electrode 8 and a discharge space 11 formed at a crossing point of the scan electrode 4 and the sustain electrode 5 form a discharge cell 12.
FIG. 2 shows a PDP electrode arrangement diagram of the PDP shown in FIG. 1. The PDP electrodes have an m×n matrix configuration. Address (A) electrodes A1 to Am are located in a column direction, and scan (Y) electrodes Y1 to Yn and sustain (X) electrodes X1 to Xn are located in a row direction, alternately. The discharge cell 12 shown in FIG. 2 corresponds to the discharge cell 12 shown in FIG. 1.
In a typical AC PDP driving method a frame is divided into a plurality of subfields and includes a reset period, an address period, and a sustain period. In the reset period, the discharge cells are reset in order to stably perform an address operation. In the address period, the cells that are turned on and the cells that are not turned on are selected on the panel, and wall charges are accumulated on the cells that are turned on (i.e., the addressed cells). In the sustain period, a discharge for actually displaying pictures on the addressed cells is performed.
In order to perform these operations, a sustain discharge pulse is alternately applied to the scan electrode and sustain electrode in the sustain period, and a reset waveform and a scan waveform are applied to the scan electrode while the sustain electrode is biased with a predetermined voltage in the reset period and the address period. Typically, a scan driving board for driving the scan electrodes and a sustain driving board for driving the sustain electrodes are separately provided, which generates a problem of installing the driving boards in the chassis base and increases the cost.
Accordingly, a method for combining the two boards into a single board to provide the same to one side of the scan electrode, and extending one terminal of the sustain electrode to reach the combined board has been proposed, but the combination increases the impedance formed at the extended sustain electrode.
To solve the problem, Korean laid-open application No. 10-2003-90370 has disclosed a method for applying a sustain discharge pulse by a scan electrode driver and minimizing a sustain electrode driver.
FIG. 3 shows a conventional PDP driving waveform in a sustain period. Voltages Vs and −Vs for a sustain discharge are alternately applied to the scan (Y) electrode (or sustain (X) electrode) in the sustain period, and the voltage at the sustain electrode (or scan electrode) is maintained at the ground voltage.
In this instance, since very few wall charges are accumulated on the cells which are not selected in the address period when the conditions for all the discharge cells are the same, no discharge is generated between the scan electrodes and the address electrodes of the discharge cells which are not selected when the voltages Vs and −Vs are applied to the scan electrode in the sustain period.
However, a misfiring may be generated between the scan electrode and the address electrode of the non-selected cells in the address period because of unstable wall charge states between the discharge cells when the voltages Vs and −Vs are applied to the scan electrode in the sustain period.
Therefore, in order to prevent the misfiring between the address electrode and the scan electrode in the prior art, the address electrode is floated in the sustain period or an address voltage Va is applied to the address electrode when the voltage Vs is applied to the scan electrode, thereby reducing the voltage difference between the address electrode and the scan electrode.
The above-described prior art reduces the voltage difference between the scan electrode and the address electrode when positive wall charges are accumulated on the scan electrodes of discharge cells which are not selected in the address period and the voltage Vs is applied to the scan electrode in the sustain period. However, a misfiring may be generated since the voltage difference between the scan electrode and the address electrode may be greater than a firing voltage when negative wall charges are accumulated on the scan electrodes of discharge cells which are not selected in the address period and the negative voltage −Vs is applied to the scan electrode in the sustain period.